The present invention relates to a composite catalyst for the purification of exhaust gas.
As a catalyst for the purification of exhaust gas, particularly NOx (nitrogen oxide), there has heretofore been known an Ir (iridium) catalyst (see U.S. Pat. No. 5,326,735 and U.S. Pat. No. 5,487,268).
The conventional Ir catalyst exhibits a relatively high capacity of purifying NOx in an atmosphere of excess oxygen but is disadvantageous in that it has a low durability.